This invention relates to a marker and guide catheter in the field of coronary and peripheral angioplasty with stenting. More specifically, this invention relates to accurate stent placement when a stenotic segment is located at a lumen opening or bifurcation of a blood vessel.
The vascular bed in humans is a complex and extensive network of lumens carrying blood and delivering oxygen and nutrients throughout the skeletal network, organs and muscle tissues of the body. At a macro level the human circulatory system can be logically characterized as originating from the heart with an ascending aorta extending from the left ventricle upwardly into an arch and then descending generally vertically downward via a central lumen column through a patient's thoracic region and diaphragm to an abdominal aorta segment. The aorta terminates with common left and right iliac arteries extending into the common femoral arteries and down into lower extremities.
In general terms the aorta provides a base for systemic circulation for the entire body. Right and left coronary branches extend from an aortic root to supply a patient's heart while an aortic arch supplies blood to the patient's head, neck and arms. Branches from the thoracic aorta supply the chest and branches from the abdominal aorta supply the abdomen while the pelvis and lower extremities are fed from common iliac arteries extending from a base region of the aorta.
The human vascular system, originating from the heart, is composed of a series of flexible lumens decreasing in diameter and increasing in branches. In broad terms a sequence of blood flow is from a left heart ventricle to an aorta, to arteries, to arterioles, to venules, to veins, and to a vena cava back to a right side of the heart. Vascular lumens are composed of elastic tissue which can, over time, become somewhat hardened in a disease zone due to an internal accumulation of cholesterol laden plaques, which is a fatty material composed of cholesterol and other particles which build up within an artery wall to create a narrowing (stenosis) of the artery. Plaque stenotic segments can decrease vessel elasticity and concomitantly occlude a free flow of blood through the lumen. This malady is sometimes referred to as atherosclerotic arterial disease.
In 1964 an vascular radiologist by the name of Charles Dotter, often referred to as the “Father of Interventional Radiology” pioneered development of angioplasty and a catheter delivered stent as a treatment for peripheral arterial disease.
Stents are now universally used in percutaneous coronary and peripheral angioplasty procedures, which effectively open narrowed blood vessels. A stent is a tiny, expandable, cylindrical wire mesh scaffolding, mounted on a deflated balloon in a “crimped” or collapsed state. It is inserted into the narrowed segment of the artery over a thin angioplasty wire via a guide catheter and then expanded by inflating the balloon.
A guide catheter is a long hollow tube which is percutaneously advanced into an opening of a coronary artery or other arteries originating from the aorta. The guide catheter allows a percutaneous injection of contrast media into the stream of a blood vessel. A thin angioplasty guide wire is advanced, through the guide catheter, into a blood vessel and inserted through the narrowed lumen stenosis. A stent (with an interior, concentric, collapsed, tubular balloon) is introduced, over the angioplasty guide wire, through the guide catheter and accurately positioned at a lumen stenosis site. High pressure (nine to eighteen atmospheres) is then used to inflate the balloon and permanently expand the stent scaffolding outwardly to radially compress plaque at the lumen stenosis segment, making an enlarged opening inside the artery for improved blood flow. The stent balloon is thereafter deflated and withdrawn through the interior of the guide catheter along with the guide wire and the expanded wire stent remains positioned as scaffolding at the stenotic site.
An interventional physician uses radiography, an X-ray procedure to identify a stenosis location and estimates the size of a diseased blood vessel and severity of stenotic plaque narrowing. Blood vessels are not visible by X-ray per se, however, by injecting a contrast media (dye) through the guide catheter a trained physician is capable of accurately viewing arterial boundaries with the pulsating flow of blood through downstream arteries and develop an accurate sense of a stenotic vessel site requiring interventional correction.
Placing a stent at a site of a stenosis in a downstream segment of a blood vessel is now considered a routine process. When plaque stenosis narrowing is located at a bifurcation opening of the blood vessel from the aorta, or at a downstream bifurcation site where a blood vessel branches, however, optimal placement of the stent is more challenging. In this, positioning a stent too distal may miss part of a narrowing stenosis while positioning a stent too proximal may result in proximal end of the stent protruding into a primary blood vessel.
Examples of challenging locations are plaque stenosis occurring at an opening of arteries originating from the aorta: the left main coronary artery, the right coronary artery, the innominate artery, left common carotid artery, left subclavian artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, the left and right renal arteries and iliac arteries. Other examples include vessel bifurcations downstream in the coronary arterial tree such as the left anterior descending and the left circumflex coronary arteries which bifurcate from the left main coronary artery. It also includes peripheral arteries such as the common femoral arteries bifurcations.
Due to the complexity of accurately positioning a stent at a vessel transition opening, in a pulsating circulatory system, stenting a stenosis at a bifurcation requires a longer operative time, exposing a patient and staff to extra radiation during the angiography, and injecting larger amounts of radiopaque contrast media which may compromise the patient's hemodynamic status and kidney functions. It is not uncommon for an interventional physician to use additional stents because of non-satisfactory initial results due to stent malposition. The procedure may therefore become prolonged and complex, carrying out higher risks and a higher rate of complications.
In order to address this problem it has been previously suggested to use a two part balloon stent catheter, where a relatively large torus part of a balloon is positioned at a proximal end of a cylindrical stent balloon. The inflated torus balloon serves as a stop at a bifurcation junction to prevent the stent on the cylindrical companion stent balloon from extending too far into a bifurcated lumen. At least one limitation of such a torus stop balloon, however, is that it will also temporarily limit or even occlude blood flow into the target blood vessel during the stent positioning. It will also block the contrast media (dye) from reaching the target vessel. The contrast media is needed to confirm the final positioning of the stent before the deployment.
To address and ameliorate the torus, stop balloon negative issues and address a desire for a more sophisticated and accurate stent placement at bifurcation junctions, the subject invention is directed to a smaller, low pressure (one or two atmospheres) arcuate marker balloon segment or segments located at a distal end of a guide catheter. The arcuate marker balloon segment or segments, will enable a free flow of blood. In addition the arcuate marker balloon will provides a specific identification of a bifurcation site to accurately position a conventional stent, using both angiography and tactile feedback, while reducing the use of contrast media.
When the stenosis is at the opening of the blood vessel, that branches from the aorta, the guide catheter is percutaneously advanced, stopping when the tip lands at an opening of the branching blood vessel. Contrast media is percutaneously injected via the guide catheter into the target vessel to view the anatomy. The angioplasty wire is then advanced in the target vessel through and past a stenotic site within the blood vessel. The stent apparatus is then advanced over the guide wire to the site of the stenosis at the opening of the blood vessel. The guide catheter tip is then pulled back into the aorta and a marker balloon segment or segments are expanded to allow stent positioning at the opening of the blood vessel.
The marker balloon segment or segments on a distal end of the guide catheter are percutaneously inflated via a small independent tube or tubes within the guiding catheter using contrast media. By the provision of angiography and tactile feedback, the guide catheter with the visible inflated marker balloon at its tip is gently advanced, to face the aortic wall and the opening of the branching blood vessel. The marker balloon segment or segments will stop the guide catheter from sliding into the branch, thus marking the aortic wall and the side branch opening. The balloon stent is then gently retracted until a radiopaque marker band on a proximal end of the balloon stent joins with the marker segment or segments on the distal end of the guide catheter as one visible radiopaque image thus indicating accurate position of the stent at a bifurcation junction of the vascular system juxtaposed at a distal end of the guide catheter marker balloon. This provides optimal positioning of the proximal edge of the balloon stent at the opening of the branching vessel. Final balloon stent position, before the stent balloon is inflated, may be confirmed by injection of contrast media via the guide catheter and past the guide catheter marker balloon segment or segments.
Inflation pressure for the arcuate marker balloon segment or segments at the distal end of the guide catheter is far less than the operating pressure of the stent balloon. While a stent balloon needs a special inflation device to reach pressures between nine and eighteen atmospheres, the subject arcuate balloon marker segment or segments are advantageously inflated to one or two atmospheres by a hand syringe. Moreover, a blood vessel wall may have a special geometry. A low pressure marker balloon arcuate segment or segments can advantageously be used to provide easier and better alignment with a main vessel wall by controlling the amount of pressure applied to a particular balloon segment.
In addition, a low pressure arcuate marker balloon segment or segments at a distal end of a guide catheter is operable to set or alter an angle of a guide catheter distal end, when inside the artery branching from the aorta, with respect to a subsequent branch lumen, to advantageously adjust the distal end angle to facilitate insertion of the angioplasty wire and a balloon stent at a difficult angle of a target blood vessel. Inflating the marker balloon within the branch lumen may also stabilize the guide catheter position without blocking the blood flow distally.
The arcuate shaped balloon segment or segments at a distal end of the guide catheter will prevent complete blocking of the blood flow when the guide catheter marker balloon or balloons are inflated. The subject marker balloon segment or segments at a distal end of the guide catheter also enables continuous monitoring of blood pressure in a patient's aorta. In this, aorta blood flowing past the low pressure marker balloon segment or segments allows measuring the aortic blood pressure, through the guide catheter tip.
The subject arcuate marker balloon segment or segments are connected to the tip of the guide catheter but do not extend a full three hundred and sixty degrees circumferentially around the distal end of the guide catheter. The arcuate shape of the subject low pressure marker balloon segment or segments will accommodate and accurately identify a wall location of the main blood vessel and opening of a side branch to the main vessel. The arcuate shaped segments, in contrast to a full circumferential configuration, will not occlude blood flow to a target vessel during a stenting procedure.
Further selective delivery of marker fluid pressure to a distal end of a guide catheter marker balloon segment or segments can be advantageously used to orient a distal end of a guide catheter with respect to an opening of a branch vessel. In a similar manner it can stabilize the position of the guide catheter in the primary vessel during complex angioplasties, while allowing continuous blood flow to the target vessel and continuous aortic pressure monitoring at the guide catheter tip.
The limitations suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness, reliability and patient satisfaction with prior guide catheter structures for angioplasty, with stenting, at bifurcation sites in a circulatory system. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that present angioplasty, involving stenting at bifurcation sites in a circulatory system, appearing in the past will admit to worthwhile improvement.